Hyponatremia and increased secretion of vasopressin induced by vincristine administration in rat.

Administration of vincristine resulted in a hyponatremic state and concurrent elevation of the plasma immunoreactive arginine8-vasopressin (IR-AVP) level in rats. Development of the vincristine-induced hyponatremia and hypoosmolality was accompanied by a loss in weight, a decreased water intake and a large reduction in the daily urine sodium excretion. The cause of the sodium loss is thought to be the diarrhea observed during vincristine treatment. Hematocrit and serum urea nitrogen levels were increased. It is concluded that the condition differs from the syndrome of inappropriate secretion of antidiuretic hormone (SIADH): the increase in plasma IR-AVP concentration may be associated with dehydration due to vincristine toxicity.